Friday, September 19, 2014

Converting your LXI instrument to a Wi-Fi enabled instrument

Its been a while and this will be the first post under our new address: gpete.blogs.keysight.com. That means that we are now an official blog for Keysight Technologies.

This will be a useful post, I'm going to show you how to easily convert your LXI enabled instrument into a Wi-Fi enabled instrument using an inexpensive travel router. The newer travel routers are very power efficient and can run from a USB port. If you have an instrument with both LXI and USB (like a 34972A), you can run a Wi-Fi router with only two cables; the USB power cable, and LAN cable from the router to the instrument. As usual, I have made a video that helps to describe the connections and how to setup your travel router and LXI instrument.




Many modern USB routers are similar, so in order to evaluate them I ordered an inexpensive TP Link TL-WR702N  This one has the added advantage of being very small.

Before your buy a travel router you need to check if they have Access Point (AP) mode and Client Mode settings. This will allow you to choose which type of connection you want to use with your PC and LXI instrument.

AP Mode



The first method uses the travel router in Access Point (AP) mode to make a simple ad hoc wireless connection between your computer and the 34972A, as shown in the figure below. This method is good for a 1-to-1 connection between your PC and instrument. 
AP Mode topology

Client Mode

The second method uses the travel router in Client Point mode to make the 34972A a client so that it can wirelessly communicate with a centralized AP through the travel router. With this technique, you can connect to your 34972A from anywhere on your network. Your computer also communicates with the same central AP, thereby giving you wireless control of the 34972A. 
Client Mode Topology

Setting up your Router


Configuring AP Mode on a Travel Router

While the specific configuration for every type of router is different, they share common steps for setting up the different modes. Here are some general steps for setting up AP mode on a travel router. If you are using the TP Link TL-WR702N, ensure that you have the router's firmware version updated to 4.19 or later. Otherwise the router will not remember these settings for more than a day. Consult your router’s manual for specifics.
  1.     On your PC, connect to the router using either a wired connection or through Wi-Fi using your router’s SSID (wireless router name) 
  2. Open an internet browser (Internet explorer, Firefox, Chrome, etc…) and type the router’s IP address. This is typically 192.168.0.1 or 192.168.0.100. Some manufacturers set default IP addresses to a non-standard address. Consult your manual for specifics.
  3. Log in using the admin credentials.
  4. Critical step: Change the Wireless mode to Access Point mode or AP mode.
  5. Change the LAN settings from DHCP to Static IP. This will change the wired connection between the router and device (e.g., your PC or the LXI instrument) to be a static address. DHCP on the wireless connections should still be enabled.
  6. Ensure that your DHCP server is running in the wireless settings.
  7. Apply and log out.
  8. Disconnect the LAN cable from the PC if you used that connection method in step 1. 

Configuring Client Mode on a Travel Router 


  1. On your PC, connect to the router using a wired connection. Disable Wi-Fi on your PC to avoid conflicts between the PC’s wired and wireless connections.
  2. Open an internet browser (Internet explorer, Firefox, Chrome, etc...) and type the router’s IP address. This is typically 192.168.0.1 or 192.168.0.100. Some manufacturers set default IP addresses to a non-standard address. Consult your manual for specifics.
  3. Log in using the admin credentials.
  4. Critical step: Change the Wireless mode to Client mode. This might reboot the router. If it does, follow steps 1-3 again once the router has rebooted.
  5. In the wireless client settings, click on a button that says “Survey” or “Wireless Survey.” This will look for available wireless connections for your router to connect to. This will connect you to the (wide area network) WAN or Internet.
  6. Enter in the security information for your WAN router’s Wi-Fi.
  7. Apply and log out.
  8. Disconnect the LAN cable from the PC.

Connect and Configuring the 34972A


  1. Wire travel router connections
    • To the LAN/WAN port, connect an Ethernet (RJ-45) cable. The other end of this cable will be connected to the 34972A LAN port.
    •  Connect the USB cable from the back of 34972A to the travel router power port to turn it on. See the measurement tip on powering your travel router for more information.
  2. Wire 34972A connections
    • To the LAN port, connect an Ethernet (RJ-45) cable. The other end of this cable should be connected to the travel router’s LAN/WAN port.
    •  An appropriate AC line cord must be used to power the 34972A.
  3. Configure the 34972A (default configuration)
    • From the front panel, the following configuration should be verified (press Shift > Interface). Repeatedly press Interface (Sto/Rcl button) to see each subsequent setting. For parameters that can be set, these are the factory default settings. Simply turn the knob to make any necessary changes.
    Wait for the travel router to assign an IP address to the 34972A. You will know this is complete when the above mentioned STAT (status) parameter shows CONNECTED and the 34972A IP address is something other than 0.0.0.0.
  4.  Turn on your computer’s wireless feature and use it to show a list of available wireless networks. Connect to your travel router’s wireless SSID (for AP mode), or your WAN network (Client mode).

That's it. You should be able to access the 34972A wirelessly by using its IP address. You can obtain the IP address from the front panel as described in step 3. You can confirm the wireless connection by opening a browser and entering the 34972A’s IP address in the URL field to access the 34972A’s built-in Web server.